# unique-field-definition-names

Source: https://apigenie.pl/docs/linter/graphql/rules/unique-field-definition-names

This rule checks that the field names of a type are unique across the type and its extensions, as the GraphQL specification requires.

## Rule Details

The rule reports the issues of the validation rule of the same name, with the messages of graphql-js. A document that breaks it is rejected by GraphQL servers and tools, so the rule should stay enabled with the `error` severity.

## Configuration

This rule has no options.

```yaml
version: "1.0"
commands:
  lint:
    graphql:
      rules:
        unique-field-definition-names: warning
```

The rule can be disabled for a node and everything nested in it with an `# apigenie-lint-disable unique-field-definition-names` comment on the node, or for a whole file with the comment at the top of the file, separated from the first definition by a blank line. It applies to definitions.

## Examples

**Good**.

```graphql
type User { id: ID! }
extend type User { name: String }
```

**Bad**. The linter reports `Field "User.id" can only be defined once.`.

```graphql
type User { id: ID! }
extend type User { id: ID }
```